The present study was approved by the ethics committee of our hospital. Family members and the patients had signed written informed consent for the examination.
We retrospectively analyzed 150 suspected TAD patients treated in our hospital from January 2014 to October 2017. Inclusion criteria: suspected TAD patients by clinical diagnosis and/or those TAD patients with an imaging diagnosis in another hospital. Exclusion criteria: ① patients who were allergic to contrast agents; ② patients who had severe heart, liver, kidney, or other diseases and could not tolerate the imaging examinations; ③ patients whose imaging quality did not meet the diagnostic requirements. Of 150 patients, 120 patients were men and 30 patients were women. Their age was 49.2 ± 10.5 years. All the patients were identified by primary hospitals and then transferred to our hospital. Generally, for patients suspected of TAD, MSCT and TTE had been completed in primary hospitals, but the CT images could not be viewed in a timely manner. Therefore, DSCT was performed again to confirm the diagnosis in our center. The primary outcomes were the sensitivity and specificity of DSCT, MSCT, and TTE. The secondary outcomes were the distance between the actual rupture site and the one diagnosed by DSCT, MSCT, and TTE, and the size of the rupture site diagnosed by DSCT, MSCT, and TTE.
Equipment and methods
The DSCT scanner was from Siemens (Germany) and could be used to perform both plain and enhanced scanning. The scan range was from the level of the first rib to the level of the pubic symphysis. The scanning parameters were as follows: rotation time 0.5 s, collimation width auto (64*0.625), pitch 0.65, reconstruction slice thickness 1.0 mm, tube A voltage 140 kV, tube B voltage 80 kV and auto mAs.
The MSCT scanner was a 64-row CT scanner from Philips (Netherlands) and was used for plain and enhanced scanning in this study. The scan range was from the level of the first rib to the level of the pubic symphysis. The scanning parameters were as follows: rotation time 0.5 s, collimation width auto (64*0.625), pitch 0.65, reconstruction slice thickness 1.0 mm, tube voltage 120 kV, and auto mAs.
In the enhanced scan of DSCT and MSCT, a high-pressure syringe was used to quickly inject contrast agent through the forearm vein, with injection rate of 4–5 mL/s and a total volume of 70 ml. When the concentration of contrast agent at the aortic root reached 100 Hounsfield units, the enhanced scanning was automatically performed. The original images were transmitted to the workstation for image postprocessing. The three-dimensional (3D) reconstruction technologies included multiplanar reconstruction (MPR) and curved planar reformation (CPR), maximum-intensity projection (MIP), shaded surface display (SSD), and volume rendering (VR).
TTE was performed using the GE-VV7 color Doppler ultrasound machine (USA) with the probe frequency of 2.5–5.0 MHz. Transthoracic and transsternal superior fossa views were obtained to observe the aortic root, ascending aorta, aortic arch, thoracic descending aorta, and abdominal descending aorta and their main branches. The lesion locations, intimal echo intensity of the dissected aorta, blood flow, and spectral characteristics in the true and false lumens of the aorta were documented in detail.
The intraoperative findings or interventional treatment results were used as the diagnostic gold standard. Knowing the actual location of the rupture plays an important role in the treatment of TAD, especially the distance from the opening of the left subclavian artery. Therefore, the distance between the measured and actual rupture was compared in this paper. Missed diagnosis and misdiagnosis of the rupture site were defined as negative diagnosis of the rupture site. The letter “a” indicates that the DSCT, MSCT, TTE, and gold-standard results were all positive; “b” indicates that the DSCT, MSCT, and TTE results were positive and the gold standard was negative; “c” indicates that the DSCT, MSCT, and TTE results were negative and the gold standard was positive; and “d” indicates that the DSCT, MSCT, TTE, and gold-standard results were all negative.
Statistical analysis was performed using SPSS 19.0 software. According to the sensitivity of DSCT, MSCT, and TTE in the diagnosis of the TAD rupture site in the preliminary survey, the sample size of 150 was calculated in order to satisfy the following criteria: α = 0.05, two-tailed test, and power = 90%. The quantitative data are expressed as mean ± standard deviation and were compared with the independent-sample t test. The qualitative data were compared with the χ2 test. P < 0.05 was considered statistically significant.